1. Field of the Invention
This invention relates to peripheral controllers and more specifically to microprogrammed peripheral controllers.
2. Prior Art
In carrying out certain types of input/output operations, it becomes necessary for a peripheral controller of a subsystem to execute a series of commands in order to complete the particular operation. For example, during system initialization, a peripheral controller can be selected as a "bootload device". When selected, the peripheral controller is required to execute those operations for reading in resident programs and data into the main store of a data processing system. In addition to this, the peripheral controller may be required to execute a series of commands as part of diagnostic or test operations.
In general, systems have included special routines in either the data processing system or in the peripheral subsystem for generating the commands necessary for carrying out operations involving execution of a series of commands. When these routines are required to be included in the peripheral controller, this results in considerable increase in the control storage, requirements of the controller. In addition to increasing control storage requirements, these arrangements can be inefficient particularly when either a number of large routines required is high or when the routines involved include a considerable number of instructions.
According, it is a primary object of the present invention to provide a method and apparatus for enabling a peripheral subsystem to execute a series of operations efficiently.
It is a further object of the present invention to provide an apparatus for enabling a microprogrammed controller to execute a sequence of commands with minimum increase in its control storage requirements.